photo by Noni Todd

I’ll be spending my vacation at home this August. What chores could I do in the garden while I have time?  Barbara D, Santa Margarita

By Ann Dozier   Master Gardener

I you’re a vegetable gardener, chores will thrust themselves upon you, what with harvesting, keeping pests under control, and maintaining a good watering schedule. You could also be starting seeds of cool-season vegetables in flats in a sheltered spot so they’ll be ready to transplant into the garden as the weather cools.

Fruit trees could be summer-pruned after harvest. Get rid of rampant growth and crossing branches. This helps keep the tree to a manageable size and opens it up to sun and air circulation.

Flowers that have slowed bloom can be pinched back to encourage a new flurry of blossoms: geraniums, begonias, impatiens, petunias, daisies, pansies and violas are all candidates for this treatment. Cut off dead hydrangea blossoms after bloom. Hydrangeas do not need to be pruned much in this climate unless you feel they are too tall – and then try to determine if your variety blooms on old wood or new wood so that you don’t cut off next year’s flowers. August is a good time to plant South African bulbs which do well here. Try babiania, freesia, and ixia, for example. You can also buy summer blooming plants like crape myrtle, butterfly bush and rose of sharon while they are in bloom to get colors you want.

Help the garden survive heat waves. Provide mulch and check your watering system to be sure it’s doing its job without wasting water. Deep-water trees that are not drought resistant to a depth of 18-24 inches; use a probe or a garden fork to judge depth of penetration. Don’t forget that your compost needs to be regularly dampened, too; it will break down quickly in warm weather if it has enough moisture.

If you have visited any of the local garden centers during the past month, you may have noticed the most amazing variety of dahlias available!  Don't miss out on viewing the dahlias at the Midstate Fair!  The BEST day to visit the dahlias in the Horticulture Still Exhibits is TOMORROW, Wednesday, July 18, 2012!  The Master Gardeners are growing some dahlias that were donated by Corralitos Gardens and we are hoping to have quite a few on exhibit this year!  I was just shuffling through some old articles and found some great advice from Master Gardener Maggie King. You may want to share some of your spectacular dahlia tubers with your neighbors!

Digging Dahlias
by Maggie King, Master Gardener

A garden full of colorful dahlias is one of summer’s greatest pleasures. As autumn comes, however, even the best-tended plants began to suffer from fungal disease and the inevitable (alas!) aging process.  A few of us may have salvaged a blossom or two for the Thanksgiving table, but in general, most dahlia plants are looking pretty forlorn about now.  Our care of these plants in the fall can greatly affect their future seasons.

Dahlias are grown from tubers which are very sensitive to cold wet soil.  In areas with mild winters, the tubers can be mulched and left in the ground through the winter, hopefully to return the next summer. Over time, if left undivided, they develop into a massive clump that sends up many weak, less productive stalks.  For this reason, most dahlia enthusiasts recommend digging the tubers up, dividing and storing them carefully through the winter and replanting them the following year.  This has the added advantage of giving us more tubers to plant and to trade with friends.

Individual dahlia growers have different techniques for lifting dividing and storing, but some general rules apply. As plants begin to fade they should be forced into dormancy by withholding water.  The stalks should be cut back and the tubers carefully removed from the ground.   They should be cleaned well and left to dry in the sun for a few days.  Damaged or diseased tubers should be removed and a fungicide applied.  Tubers can either be divided at this point or stored and divided in the spring.  Regardless, they should be stored in a cool dark location buried in peat moss, vermiculite or sawdust, checked on periodically, and misted lightly if they appear to be drying out.  Dividing should be done carefully, with an eye present in each section.

The extra time and effort spent caring for dahlias in this way will pay bountifully next summer when the garden is full of these extraordinary blooms.  For additional information contact the Master Gardeners.

And on a side note, Dr. Joe Sabol said that if you leave them in the ground, you may dig them out in the early spring while the sprouts are tiny.  Each one of these sprouts are an "eye" and you must have an eye on each tuber to have a stem initiate.  It takes out some of the guess work when dividing the tuber.  Sadly, there's always some tubers that just don't survive when dividing dahlias, but the rewards make it all worth it!  Happy Gardening!

It's always in the summertime that we get inundated in calls at the Helpline about dying redwoods.  I was just going through my archives and found a great answer to an incoming email about dying redwoods.  Because water is such a valuable resource, I won't just hint around about it, but redwoods are native to areas of California that have about 40 inches of rainfall per year, mild weather and heavy amounts of fog.  Average rainfall in Paso Robles is about 15 inches, low humidity and often has very sandy/silt soil that drains quickly.

Here's the question:

Dear Mary,

We are still trying to find a solution to our dying redwood trees. The irrigation schedule is now 2 gals per tree, per day, 4 days a week.  The trees were shipped in 15 gallon plastic containers.   The trees were planted with sufficient room for root growth and to allow for the planting mix to be placed at the base of the hole, as well as around the tree.  The planting mix was approx. 20% compost, 80% natural soil.   We have had some hot weather lately.  What effect can this heat have on these trees?  I appreciate your feedback.

Thank you,

C

Answer:

There are procedures for determining the water needs of plants in a landscape.  Your particular situation on the edge of the Nipomo Mesa in a coastal area means that exposure is going to bring up the water needs of the plants.  Additionally, redwoods are high water demand plants and obtain much of their needed water from fog drip.  Somewhat more limited in your exposure.

We can estimate these conditions numerically, and what those calculations indicate is that your redwood trees will use about 3/4 of the water that a lawn planted on the same total area would use.  Now we do have good data on the water needs of a clipped grass lawn in these coastal areas, and the requirements are about 4.6 inches of water during July.  So your trees are need about 3.5 inches of water.  Think of it like a rain gauge but upside down. That's a tough concept to convert to how long to run your drip system. 

You can calculate the area for each tree, and we know that it takes a little over 27,000 gallons of water to cover an area 209' by 209' (an acre).  If you convert that 3.5 inches of water, corrected for the efficiency of the irrigation system and for the spacing of your trees, that means each tree is using about 10 gallons of water per day.  Yes, per day.

Your weekly irrigation amounts are 8 gallons per tree per week, but the tree needs 70 gallons per week.  For a period of time, the tree will be able to use water that is stored in the soil from winter rainfall.  We know that in most sandy soils, there is about 1 gallon of water per cubic foot of soil.  The later the spring rains and the greater the number of foggy days, the less water you need to apply with the drip system.  We did have some later spring rains, but it has been clear and hot most of June and July.

Redwoods benefit from less frequent deeper water than will be supplied with short irrigations.  So having said all of this, here is my recommendation.

1) Identify 2 trees - one that is doing well, and one that is just starting to look like it's suffering.  Don't pick a 'dying' tree because it's likely already gone.

2) Run your irrigation system for the normal two hour set.  Wait until the next day before going to step 3.

3) Start about 2 foot from the edge of the canopy of both trees and dig a trench towards the trunk that goes down at least 2 feet if not more.  Look for moist soil and roots.  If there is adequate soil moisture, you will be able to form a ball with the soil when you hold it in your hand.  If the soil moisture is low, then you won't be able to form a ball.  You should find roots from the tree throughout the trench. Fill in the trenches.

4) Next, run your irrigation system for 6 hours and repeat the above on the other sides of the same trees on the day following the irrigation.  Look to see how much more water movement you've gotten from this longer irrigation.  This irrigation would be supplying enough water for the tree for one day.

Let me know what you find, and if you can send pictures that'd be great!

Mary B.

Master Gardeners Offer Workshop on Fire Safe Landscaping

by Terri Sonleitner Law
UC Master Gardener

Q. What can I do in my landscape to make my home less vulnerable to
wildfires? John B., Paso Robles
A. That’s a timely question. Wildfires can be threatening, but with proper
planning you can have a beautiful landscape and create a Fire Safe Zone
around your home.
Begin by creating and maintaining a defensible space of 100 feet around
your home that includes a lean, clean and green zone of 30
feet, plus a reduced fuel zone of 70 feet. Greater defensive zones are
necessary if your home is on a steep slope or in a windswept area. Here’s
a closer look:
Green zone: Remove flammable vegetation and combustible materials
within 30 feet immediately surrounding your home. This includes keeping
trees trimmed, removing needles and leaves from roof and gutters, and
removing dead or dying plants, leaves and debris. Increase spacing
between plants, and use fire resistant plants. Regular maintenance like
pruning, weed control and adequate irrigation is necessary to maintain the
fire resistance of your landscape.
Reduced fuel zone: Create this next to the green zone, extending out
an additional 70 feet, or to your property line. Open space between plants
improves chances of stopping a wildfire. Either create greater horizontal
and vertical spacing between plants, or if you have trees, remove plants
growing beneath the trees that are greater than 4 inches in height. Remove
lower limbs of trees to at least 6 feet, and remove one-third of branches on
any smaller trees.
The Master Gardeners, with assistance from the Fire Safe Council, San
Luis Obispo County, installed a new Fire Safe Landscape display in our
demonstration garden. Our free July workshop will focus on Fire Safe
Landscaping this Saturday from 10 a.m. to noon in the Garden of the
Seven Sisters, 2156 Sierra Way in San Luis Obispo. Parking is free in the
adjacent parking lot. Additional information on Fire Safe Landscaping is available from the Fire
Safe Council: http://www.fscslo.org/Solutions.html# and from University of
California
publications:http://firecenter.berkeley.edu/docs/CeMasterGardener8322.pdf

Have a Gardening Question?
Contact the University of California Cooperative Extension Master
Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-
7190 from 10 to 12 p.m. on Wednesday in Arroyo Grande; and at 434-4105
from 9 to 12 p.m. on Wednesday in Templeton. Visit the UCCE Master
Gardeners Web site athttp://ucanr.org/sites/mgslo/ or e-mail
mgsanluisobispo@ucdavis.edu